Quantitative results are obtained by building a Computable General Equilibrium model in the mathematical programming language General Algebraic Modelling System (GAMS). Four scenarios are simulated: 1) import tariffs reform; 2) improvement of exports access; 3) improvement of investment climate and 4) the scenario that combines previous three, or a full WTO accession. This research studies the accession of a developing country to the World Trade Organisation on the case of Ukraine. By contrast, output and household consumption levels vary from scenario to scenario. The results of the model show that in all scenarios there is growth of both exports and imports. Thus, with expanded trade and practically the same output and consumption, Ukraine merely becomes more open and shifts to foreign trade. In the third scenario, improvement of investment... The first two simulations, tariff reform and improvement of export access, show no significant change in domestic production and consumption.